Pretargeting protocols for enhanced localization of active agents to target sites

Abstract

Methods, compounds, compositions and kits that relate to pretargeted delivery of diagnostic and therapeutic agents are disclosed. In particular, methods for radiometal labeling of biotin and for improved radiohalogenation of biotin, as well as related compounds, are described. Also, clearing agents, anti-ligand-targeting moiety conjugates, target cell retention enhancing moieties and additional methods are discussed.

What is claimed is: 
     
       1. A method of prolonging active agent retention at a target cell site in a mammalian recipient, wherein the active agent is a radionuclide, which method comprises administering to the recipient a conjugate comprising a targeting moiety, which binds to an antigen expressed on the target cells and which targeting moiety comprises an antibody or an antigen-binding antibody fragment, streptavidin and said active agent comprising a radionuclide, wherein the active agent is directly or indirectly associated with streptavidin rather than said antibody or antibody fragment comprising targeting moiety, thereby providing for prolonged radionuclide retention at the target cell site. 
     
     
       2. A method according to claim 1 wherein the radionuclide active agent is bound directly to streptavidin, or is bound to streptavidin through a chelate, or is associated with streptavidin through biotin binding. 
     
     
       3. A method according to claim 1 wherein the radionuclide is selected from the group consisting of Re-186, Re-188, Y-90, At-211, Pb-212, Bi-212, Sm-153, Eu-169, Lu-177, Cu-67, Rh-105 and I-131. 
     
     
       4. A method according to claim 1 wherein the step of administering the conjugate is conducted by intralesional or intraarterial injection. 
     
     
       5. A method according to claim 1 wherein the targeting moiety comprises a chimeric antibody or fragment which binds the same antigen as NR-LU-10 and the active agent comprises a  99m  Tc-chelate-biotin conjugate. 
     
     
       6. A method according to claim 5 wherein the chelate contained in the  99m  Tc-chelate-biotin conjugate contains an N 3  S chelating core. 
     
     
       7. A method according to claim 6 wherein the N 3  S chelating core is attached to biotin by an amide linkage. 
     
     
       8. A method according to claim 1 wherein said method is a diagnostic method and the radionuclide is used to detect the presence of target cells. 
     
     
       9. A method according to claim 8 wherein the method of diagnosis comprises tumor imaging.